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GAGE.

APPLICATION FILED 1AN.2|. me;

Patented May 6, 1919q ses EDGAR H. BRISTOL, 0F FOXIBORO, MASSAHSTTS;

GAGE.

Lsoaois.

Specification df Letters Patent.

Patented May 6, 1919.

Application led January 21, 1918. Serial No. 212,870.

To all whom it may concern Be it known that I, EDGAR H. BRISTOL, a. citizen of the United States, and resident of Foxboro, in the county of Norfolk and Commonwealth of Massachusetts, have in-` vented an Improvement in Gages, ofwhich the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like parts.

This invention relates to gages, the particular embodiment here shown being an instrument adapted to indicate by means 0f the usual dial and pointer the algebraic sum of two fluid pressures. `My invention will best be understood by reference to the following description of the specific form chosen `for illustration inthe accompanying drawings wherein: v

Figuregl is a front elevation of the gage;

Fig. 2 is a similar View with the bezel, hand and dial plate removed;

Fig. 3 is a bottom view of Fig. 2 with parts broken away to disclose the fluid conducting passages;

Fig. 4l is a central vertical section;

Fig. 5 is a detail to be referred to; and

Fig. 6 is an enlarged section on line.6-6 of Fig. 3 with parts separated.

Referring to the drawings, the gage' here shown embodies a cylindrical case 7 of usual form which may have the flange 9.

for securing it in position, which case 1S closed at its front end by a bezel 11 and glazing 13 through which the indicating hand 15 may be inspected.

Referring Fig. 4, the interior of the case 7 is divi ed into two pressure receiving chambers by means of a partition plate 17. The interior of the case may be provided with a shoulder 19 to receive thisv plate which mayl be pressed against the same y the threaded ring 21. A suitable packin 23 interposed between the plate and shou der assures an airtight closure, thus providing at the rear of the casing a pressure receiving chamber cpmpletely sealed except as hereinafter described. Preferably, as shown in 'Fig 4, suitabley packing 25 is interposed between the front of the case and the glazing so as to form a second sealed chamber exterior to the plate 17.

The plate 17 1s provided withan aperture 27 and carries an expansion member 29 having a port or opening 31 registering with the aperture 27 in the plate. This expansion member may be of the well known type herein shown, consisting of a set of diaphragms having a restraining member 33 at one side thereof, so that when the member is distorted by pressure it will move angularly.

It will be readily understood by inspection of Fig. 4 that the interior of the expansion member 29 is in communication by the openings 27 and 31'. with the chamber on the outer side of the plate 17 and forms in effect a part thereof. Any distortion ofthe-tube therefore will correspond to and measure the differential of two pressures adlmitted respectively to the chambers in front of and in back of this plate 17.

To indicate these pressures, for lexample by means of an index hand such as 15, an arm 35 may be secured to the free end of the expansion member 29, this arm extending outwardly through the opening -or port 31 and the aperture 27 and being connected 'in any suitable manner to transmit the'motion of the free end of the tube to the 'index hand 15. AHerein (see Fig. 2) the end .of the arm, which is conveniently offset as shown in Fig. 5, is connectedy by a link 37 to a sector gear 39 adapted to mesh with a pinion on the index shaft. 'As shown in Fig. 4, the index carrying shaft and the segment may be mounted directly on the outer side 'of the partition plate 19. 4The connection 'just described should be such as to minimize friction.V Herein the link 37 is of wire having a hooked end entering an aperture 41 (Fig. 5) in the arm 39 and as shown in Fig. 5 the margin of the opening is preferably rounded to permit free movement of the round wire of the link.

-As shownin Fig. 3, pressure may be admitted to the chamberin the rear of the plate 17 by means of an opening 43 and to` the chamber forwardly of that plate by a vpassage 45 formed in the case and prefertively, as indicated in Fig. 4. The ends of these passages are shouldered to receive packin. rings 51 which are compressed between ie flange 50 and the shoulders (con` trast Fig. 6 and Fig. 4). A firm sealed joint is thus provided while a large bearing surface between the flange and the casing prevents movement or distortion of the parts in use. AThe pipes may be fastened by means of screws 53 passin through the flange portion 5() and tapped into the case 7. Preferably one pipe, as 47 (Fig. `6), is made longer than the other. It is then impossible to assemble the parts incorrectly as the long pipe would not go home in the opening 45.

In the above description I have described the instrument as adapted for measuring two pressures each of which might vary from that of the atmosphere and for this purpose the joint formed at the partition 17 and the joint of the glazing 13 are both packed. Obviously, however, one of the two pressures might be atmospheric pressure and in this case the device would function as an ordinary rather than as a differential gage.

It will be seen from the above description of an illustrative embodiment of my invention that I have provided a simple and sub stantial device, that the joints thereof are large\ and as they do not involve moving parts are easily sealed against the escape of fluid.

My invention might obviously be embodied-in other forms than that specifically illustrated, which, however. serves 1by way of an example.

What I claim as newand desire to secure by Letters Patent is:-

1. An instrument af the class described,

including a pair of chambers having a separating wall between them, means to admit pressures to the chambers respectively, a closed expansion member in one chamber, there being a communicating passage between the interior of said member and the other chamber, indicating means in said other chamber and motion transmitting means between said member and the indicating means extending through said passage. f

2. An instrument of the class described, comprising a casing, an airtight partition dividing said casing, means to admit different pressures to the opposite sides of said partition, an expansion tube on said partition, said partition having an opening communicating with the interior of the tube, an arm carried by said tube extending through the opening, indicating'devices car ried on said partition and connected to said arm to be moved thereby.

3An instrument of the class described` comprising a casing having an internal shoulder, a plate to seat on said shoulder, sealing means therefor, an airtight glazing and bezelfor said case, said case having fluid admission openings leading to opposite sides of said plate, said plate having an opening, au expansion tube on one side of said plate having an opening registering with said aperture and an indicating de vice connected to said tube through said aperture.

In testimony whereof, I have signed mv name to this specification.

EDGAR H. BRISTOL. 

